Crystal Structure of SrAl2B2O7 and Eu Luminescence

The crystal structure of strontium dialuminodiborate SrAl₂B₂O₇ has been established by single-crystal X-ray diffraction methods. The compound crystallizes in the trigonal system (space group R c, Z=6) with cell parameters a=4.893(1) Å and c=47.78(1) Å. Aluminium and boron atoms are, respectively, in tetrahedral and triangular oxygen coordination. The assembly of Al₂O₇ units and BO₃ triangles forms double layers between which Sr²⁺ ions are located. The Eu²⁺-doped crystalline powder exhibits a luminescence band with maximum at 415 nm. Luminescence characteristics are compared to those of other strontium borates.     

Quantum efficiency of double activated Tb3Al5O12:Ce, Eu

The quantum efficiency and luminescence properties of double activated terbium aluminum garnet samples were investigated in the present study. A mathematical procedure and PL measurement system are developed for express analysis of quantum efficiency of luminescent materials. The energy-level diagram was proposed to explain the luminescence mechanism. Application of TAG:Ce,Eu with improved CIE and CRI in LED device is demonstrated.     

高掺杂Ce,Gd(Y_(3-x-y)Ce_xGd_y)Al_5O_(12)荧光粉的发光下降及温度猝灭特性

采用高温固相法分别合成了不同Ce浓度掺杂的和固定Ce浓度为0.06不同Gd浓度掺杂的Y3Al5O12(YAG)系列荧光粉,通过测量其激发、发射光谱、漫反射光谱、荧光寿命和变温发射光谱,研究了掺杂元素的浓度对荧光粉发光性能的影响以及荧光粉发光的温度猝灭性质。研究结果表明:荧光粉发光强度随着Ce3+掺杂浓度和Gd3+掺杂浓度的提高均呈下降趋势。分析发现,荧光粉发光强度下降并非主要由浓度猝灭所引起,而是由于高浓度掺杂下发生YAG基质与Ce3+对激发光的竞争吸收,导致Ce3+对激发光的吸收量减少,从而影响发光强度。温度实验表明,随着温度的升高,荧光粉发光强度下降。Ce含量的改变对YAG:Ce荧光粉的热猝灭性质影响较小,Gd的掺杂使荧光粉的发射波长向长波方向移动,同时热猝灭现象严重。     

Sm2O3Ga2O3 and Gd2O3Ga2O3 phase diagrams

Four definite compounds exist in the Sm₂O₃Ga₂O₃ binary phase diagram, namely: Sm₃GaO₆, Sm₄Ga₂O₉, SmGaO₃, and Sm₃Ga₅O₁₂. The $\text{3}\text{1}$ compound is orthorhombic (space group Pnna - Z.4) with the cell parameters: a = 11.40₀Å, b = 5.51₅Å, c = 9.07Å and belongs to the oxysel family. Sm₃GaO₆ and SmGaO₃ melt incongruently at 1715 and 1565°C; Sm₄Ga₂O₉ and Sm₃Ga₅O₁₂ have a congruent melting point at 1710 and 1655°C. With regard to the Gd₂O₃Ga₂O₃ system three definite compounds have been identified: Gd₃GaO₆, Gd₄Ga₂O₉, and Gd₃Ga₅O₁₂. Only the garnet melts congruently at 1740°C with the following composition: Gd_3.12Ga_4.88O₁₂. Gd₃GaO₆, and Gd₄Ga₂O₉ melt incongruently at 1760 and 1700°C. GdGaO₃ is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram.     

Al18B4O33:Eu,Tb单基双掺杂荧光粉的制备及发光性能

以柠檬酸为络合剂,采用溶胶-凝胶法成功制备了Al18B4O33:Eu,Tb荧光粉.采用热分析仪、X射线衍射仪和扫描电镜分别对样品进行了热分析、结构和形貌分析,采用荧光光谱仪和亮度计测试样品的激发发射光谱和亮度.结果表明:前驱体先经700℃预烧,然后再于1100℃煅烧3h后,可获得粒度分布均匀、结晶性良好的Al18B4O33:Eu,Tb荧光粉;共掺杂Eu和Tb的Al18B4O33荧光粉可同时发出“三基色”所需要的特征发光;该荧光粉中同时存在Eu2+离子、Tb3+离子和Eu3+离子,在350～ 400 nm之间的紫外区域存在较强的激发峰,可被用于与紫外LED复合合成白光LED;通过研究Eu和Tb的掺杂量对荧光粉发光强度的影响发现,适量调节Eu和Tb的掺杂量可以改变Al18B4O33:Eu,Tb荧光粉的发光颜色和强度.     

Solvothermal synthesis and luminescence properties of monodisperse Gd2O3:Eu and Gd2O3:Eu@SiO2 nanospheres

A series of uniform, monodispersed Gd(OH)³:Eu³⁺ nanospheres less than 100 nm were successfully synthesized with iron ions as catalyst and DMF as solvent under the solvothermal condition. Cetyltrimethyl ammonium bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as co-surfactant during this facile procedure should be changed as A series of uniform, monodisperse Gd(OH)³:Eu³⁺ nanospheres less than 100 nm in diameter were successfully synthesized with solvothermal method. Iron ion was used as catalyst and Dimethylformamide (DMF) as solvent, Cetyltrimethyl Ammonium Bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as surfactants. Further calcination process was applied to prepare Gd₂O₃:Eu³⁺ nanoshpheres during this facile procedure.     

Luminescence in trilanthanumtrichlorotungstate (La3WO6Cl3)

The luminescence properties of La₃WO₆Cl₃ are reported and discussed. The tungstate group occurs as a trigonal prismatic WO^6?₆ complex. The blue luminescence is, for the greater part, quenched at room temperature. No energy migration occurs in this lattice. The decay times are discussed in terms of a simple molecular-orbital (MO) scheme. The luminescence of the following activating ions was studied: Mo⁶⁺, Bi³⁺, Eu³⁺, Sm³⁺, Ce³⁺, and Tb³⁺. The molybdate group produces a red emission with low efficiency. The Bi³⁺ ion induces a narrow band emission with small Stokes shift. This is interpreted using a Bi³⁺O^2?W⁶⁺ charge-transfer state. Except for Ce³⁺, the rare earth activators show luminescence, but the total transfer efficiency from tungstate to the rare-earth ions is low. This is not due to the one-step tungstate-rare-earth transfer (which is efficient), but to the localized nature of the tungstate excitation. The Eu³⁺ charge-transfer band is at very low energies.     

CaSb2O6:Bi3+,Eu3+荧光粉的制备和发光性质

采用共沉淀法及1 200 ℃后续煅烧4 h,成功制备了CaSb₂O₆:Bi³⁺,Eu³⁺荧光粉,并对其结构及发光性能进行了研究。所制备荧光粉颗粒为六边形类圆饼状,平均尺寸在100~600 nm之间。对CaSb₂O₆:Bi³⁺,Eu³⁺发光的机理分析表明,Bi³⁺对Eu³⁺的发光存在高效的敏化与能量传递。当Bi³⁺和Eu³⁺的掺杂浓度分别为0.5%和8%,Eu³⁺位于580 nm(⁵D₀→⁷F₀ )处的荧光发射显著增强,Bi³⁺,Eu³⁺共掺样品的荧光强度是CaSb₂O₆:Eu³⁺的10倍左右。调节Bi³⁺/Eu³⁺离子掺杂比,色坐标呈现了从蓝、白光到红光的变化,表明该荧光粉可分别作为蓝或红色荧光粉使用,甚至可实现从蓝、白光到红光的自由调控,这为白光LED荧光粉的发展提供了参考。     

Garnet-perovskite transformations in the Sm2O3Ga2O3 and Gd2O3Ga2O3 systems

The effect of heating garnet melts to various temperatures has been investigated. The previously reported decomposition of the garnet phase due to loss of Ga₂O₃ was corroborated. However, it was also observed that when gallium oxide loss is prevented and the maximum temperature of the melt exceeds a critical value, phase separation of garnet to perovskite and β-gallium oxide occurs:

$\text{RE}{}_3\text{Ga}{}_5\text{O}{}_{12}\text{?3RE}\text{GaO}{}_3\text{+}\text{Ga}{}_2\text{O}{}_3$

.The reverse reaction will occur by reheating the two-phase mixture to the garnet melting point.     

Tb3+在燃烧法制备的CaLaAl3O7粉体中的发光性能

采用柠檬酸燃烧法制备了稀土TB3 掺杂的CaLa1-xAl3O7:xTb3 发光材料的前驱粉末,在低于700℃退火处理时,得到非晶态样品,而高于800℃退火处理后为纯相的CaLa1-xAl3O7:xTb3 粉末样品.通过三维荧光光谱、激发光谱和发射光谱研究了Tb3 在CaLaAl3O7基质中的发光性能及Tb3 掺杂量、退火温度和柠檬酸与金属离子的配比等对发光强度的影响.结果显示.非晶态和晶态CaLa1-xAl3O7:xTb3 品都可发光,在240 nm波长光的激发下,CaLaAl3O7:Tb3 粉体产生Tb3 的特征发射峰,归属于5D4-7FJ(J=6,5,4,3)跃迁,主发射峰位置均在543 nm处(5D4-7F5跃迁),随着粉末逐渐成相5D4-7F5跃迁明显增强.     

Non-centrosymmetric Ba3Ti3O6(BO3)2

The compound previously reported as Ba₂Ti₂B₂O₉ has been reformulated as Ba₃Ti₃B₂O₁₂, or Ba₃Ti₃O₆(BO₃)₂, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO₃:BaTiB₂O₆ (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F²)=0.039 for 504 unique reflections. Ba₃Ti₃O₆(BO₃)₂ is isostructural with K₃Ta₃O₆(BO₃)₂. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba₃Ti₃O₆(BO₃)₂ is equal to 95% of that of LiNbO₃.     

La7O6(BO3)(PO4)2:Eu3+/Tb3+荧光材料的制备及其光致发光性能

采用优化的高温固相方法制备了稀土离子Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La₇O₆（BO₃）（PO₄）₂：Eu³⁺材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为⁵D₀→⁷F₂特征能级跃迁,Eu³⁺的最优掺杂浓度为0.08,对应的CIE坐标为（0.610 2,0.382 3）;La₇O₆（BO₃）（PO₄）₂：Tb³⁺材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb³⁺的⁵D₄→⁷F₅能级跃迁,Tb³⁺离子的最优掺杂浓度为0.15,对应的CIE坐标为（0.317 7,0.535 2）。此外,对2种材料的变温光谱分析发现Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂荧光材料均具有良好的热稳定性。     

Preparation and Luminescence Behavior of CaSiO3：Eu^3＋（Bi^3＋）

CaSiO3：Eu0.08^3＋Bi0.002^3＋ with a monoclinic perovskite structure was synthesized by using sol-gel method, and its luminescence characteristics were investigated. From the excitation spectrum, it can be seen that the main peaks located at 238,396,415,437 and 359 nm correspond to the charge-transfer band of Eu^3＋-O^2- , the absorption transitions of ^7F0.1→^3L6, ^7F0→^5D3, ^7F1→^5D3 of Eu^3＋ ions, and ^3P1→^1S0 of Bi^3＋ ions, respectively. When the samples were excited with a light of wavelength 359 or 395 nm, it can be seen from the emission spectrum that the electronic dipole transition located at 609 nm corresponding to ^5D0→^7F2 of Eu^3＋ ions was stronger than the magnetic dipole transition located at 587 nm corresponding to ^5D0→^7F1 of Eu^3＋ ions, which shows that more Eu^3＋ ions were located in nonreversion center lattices. The energy transfer from Bi^3＋ ions to Eu^3＋ ions in the phosphor was also discussed. The results show that Eu^3＋ ions could be well sensitized by ^3＋ions, and the energy-transfer pattern between Bi^3＋ ions and Eu^3＋ ions was resonance energy transfer.     

Conversion de UF6 appauvri en U3O8

Uranium hexafluoride (UF₆), to or from isotopic enrichment plants is stored and transported, as a solid, in tanks containing 2 to 12 metric tons of material. Sampling must be carry out after complete melting obtained by heating of the tank. This sampling process is difficult and hazardous by risks of local solidification (sealing), of reaction with air moisture (Fluorhydric Acid, highly corrosive and toxic is formed), of chemical and radioactive contamination (in case of leaking), of loss of expensive material (especialy if enriched UF₆), and of over-filling of sampling pot (possible domage during warming up of itagain).The described new device was concepted and developed by COGEMA Laboratories and is used for two years in sampling facilities of enrichment plant of PIERRELATTE. It permits to warrant sample validity and eliminate all the hereabove risks.It allows seeing and adjusting volume of the samples and their flow, and permits measurement of temperature and pressure, specified for UF₆.This new device is usable for many others materials which present some risks and difficults, as Fluorine and its derivates, chlorine, liquefied inflammable gases etc.     

Eu3+在Ba2TiSi2O8中的发光

The barium titano-silicate phosphors doped with Eu³⁺ were synthesized by high temperature solid state reaction. The structures of as-synthesized samples were characterized by powder XRD. The maximum peaks of emission spectra of Ba₂TiSi₂O₈ and Ba₂TiSi₂O₈∶Eu³⁺ were respectively located at 450 and 618 nm, coming from the transitions of charge-transfer bands of Ti⁴⁺-O^2- and forced electric-dipole transition ⁵D₀-⁷F₂ of Eu³⁺. The luminous mechanisms of Ba₂TiSi₂O₈ and Ba₂TiSi₂O₈∶Eu³⁺ were suggested. The effects of concentration of Eu³⁺ on the luminous performance of Ba₂TiSi₂O₈∶Eu³⁺ were also studied and the results showed that the optimum concentration of Eu³⁺ was 0.12 mol per mole of matrix.     

Luminescence and vibrational spectra of Ba5Li2W3O15

The infrared and Raman spectra of Ba₅Li₂W₃O₁₅ are reported down to 200 cm^?1. From the internal stretching modes of the tungstate octahedra the crystallographic order between lithium and tungsten in the face-sharing octahedra can be derived. The green tungstate luminescence shows a low quenching temperature that is described with the Dexter-Klick-Russell model. The U⁶⁺ ion shows a yellow emission in Ba₅Li₂W₃O₁₅. There is ample evidence for two different U⁶⁺ centers with different decay times (10 and 80 μsec) and different emission and excitation spectra. One of these is located in a single layer of tungstate octahedra, the other in a double layer of octahedra.     

Synthesis of SiO2/Y2O3:Eu core-shell materials and hollow spheres

The SiO₂/Y₂O₃:Eu core-shell materials and hollow spheres were first synthesized by a template-mediated method. X-ray diffraction patterns indicated that the broadened diffraction peaks result from nanocrystals of Y₂O₃:Eu shells and hollow spheres. X-ray photoelectron spectra showed that the Y₂O₃:Eu shells are linked with silica cores by Si-O-Y chemical bond. SEM and TEM observations showed that the size of SiO₂/Y₂O₃:Eu core-shell structure is in the range of 140-180 nm, and the thickness of Y₂O₃:Eu hollow spherical shell is about 20-40 nm. The photoluminescence spectra of SiO₂/Y₂O₃:Eu core-shell materials and Y₂O₃:Eu hollow spheres have better red luminescent properties, and the broadened emission bands came from the size effects of nanocrystals composed of Y₂O₃:Eu shell.     

Controlled synthesis and luminescent properties of Eu(Eu), Dy-doped Sr3Al2O6 phosphors by hydrothermal treatment and postannealing approach

In this work, Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors have been prepared by hydrothermal treatment and subsequently postannealing approach, using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, and CO(NH₂)₂ as starting materials. The as-obtained phosphors were characterized by means of XRPD, FESEM, and PL techniques. In addition, many reaction parameters were studied in detail, including the initial mole ratios, hydrothermal reaction temperature, calcination temperature and calcination atmosphere. Remarkably, two scientific merits exist herein: Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors can be selectively obtained in a reducing atmosphere (H₂/Ar, 20%+80%) and in air, respectively; adding certain amount of sodium citrate can alter the shape and size of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors in essence. Besides, the luminescent properties of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors were studied by excitation spectra, emission spectra and decay curves.     

Luminescence of Mn2+ in SrGa12O19, LaMgGa11O19, and BaGa12O19

Lattice parameters are given of SrGa₁₂O₁₉, BaGa₁₂O₁₉, and LaMgGa₁₁O₁₉, three new gallates with the magnetoplumbite structure. The luminescence of the compounds without and with activation by Mn²⁺ is reported. The quantum efficiencies of the Mn²⁺ phosphors are between 15% (BaGa₁₂O₁₉:Mn) and 70% ({Sr_1?xLa_x}Ga_12?xMg_xO₁₉:Mn). The emission strongly resembles that of Mn²⁺ in MgGa₂O₄. The fine structure of the Mn²⁺ emission band at 77°K is due to phonon coupling.